Test to see if an image exists in C#

Question

I am writing a diagnostic page for SiteScope and one area we need to test is if the connection to the file/media assets are accesible from the web server. One way I think I can do this is load the image via code behind and test to see if the IIS status message is 200.

So basically I should be able to navigate to within the site to a folder like this: /media/1/image.jpg and see if it returns 200...if not throw exception.

I am struggling to figure out how to write this code.

Any help is greatly appreciated.

Thanks

Answer 1

Just use HEAD. No need to download the entire image if you don't need it. Here some boilerplate code.

HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create("url");
request.Method = "HEAD";

bool exists;
try
{
    request.GetResponse();
    exists = true;
}
catch
{
   exists = false;
}

Answer 2

I'd look into an HttpWebRequest instead - I think the previous answer will actually download data, whereas you should be able to get the response without data from HttpWebRequest.

http://msdn.microsoft.com/en-us/library/456dfw4f.aspx until step #4 should do the trick. There are other fields on HttpWebResponse for getting the numerical code if needs be...

hth Jack

Answer 3

I've used something like this before, but there's probably a better way:

try
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://somewhere/picture.jpg");
    request.Credentials = System.Net.CredentialCache.DefaultCredentials;
    HttpWebResponse response = (HttpWebResponse)request.GetResponse();
    myImg.ImageUrl = "http://somewhere/picture.jpg";
}
catch (Exception ex)
{
    // image doesn't exist, set to default picture
    myImg.ImageUrl = "http://somewhere/default.jpg";
}

Answer 4

You have to dispose of the HTTPWebResponse object, otherwise you will have issues as I have had...

    public bool DoesImageExistRemotely(string uriToImage)
    {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uriToImage);

            request.Method = "HEAD";

            try
            {
                using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
                {

                    if (response.StatusCode == HttpStatusCode.OK)
                    {
                        return true;
                    }
                    else
                    {
                        return false;
                    }
                }
            }
            catch (WebException) { return false; }
            catch
            {
                return false;
            }
    }